Conventionally, there are navigation devices, portable telephones and similar which provide navigation of routes for vehicles and persons using position information from the GPS (Global Positioning System).
Upon receiving position information from the GPS, multi-path caused by buildings and other obstacles often prevents from receiving position information correctly, causing a positioning error of about 100 meters.
Regarding to prevent such a problem, Japanese Patent Laid-open No. 2000-180191 discloses a navigation device, which calculates its estimating position using a travel distance and an angular shift amount, calculates the distance between its position and receiving satellite, and detects multi-path by comparing a signal traveling time of the GPS signals and the calculated distance. If multi-path interference is detected, the position is not corrected according to information from the GPS. This allows to prevent an increase of the position correction error caused by multi-path interference.